The new Hydrangea cultivar is a product of a planned breeding program conducted by the inventors, at a commercial nursery in Melle, Belgium. The objective of the breeding program was to produce new Hydrangea varieties with compact habits and strong blooming beginning in the first year. The cross resulting in this new variety was made during Summer of 2003.
The seed parent is the unpatented variety Hydrangea serrata ‘Bluebird’. The pollen parent is the unpatented variety Hydrangea macrophylla ‘Mariesii Perfecta’. The new variety was identified as a potentially interesting selection in the Summer of 2007, at a commercial greenhouse in Melle, Belgium.
Asexual reproduction of the new cultivar ‘ILVOCLOU’ by vegetative soft wood cuttings was first performed during the Summer of 2016, at a commercial greenhouse in Melle, Belgium. Subsequent propagation has shown that the unique features of this cultivar are stable and reproduced true to type in 6 successive generations.